Motor vehicle catalysts should be replaced regularly
Motor vehicle exhaust pollution is serious. However, at the “Breathing Together, Sharing Responsibility, Atmospheric Compound Pollution and Motor Vehicle Emission Control” Environmental Science Salon, Professor Wang Jianxin of Tsinghua University’s Department of Automotive Engineering said that gasoline motor vehicles can purify more than 99% of pollutants in their exhaust by using triple-acting catalysts.
A triple-action catalyst is a catalytic converter installed in the engine exhaust system that oxidizes and reduces hydrocarbons, carbon monoxide and nitrogen oxides in motor vehicle exhaust to harmless carbon dioxide (CO2), nitrogen (N2) and water vapor (H2O) prior to emission.
Pollution emissions from in-use vehicles are very low over the life of the catalyst. Once the catalyst expires and is not replaced, phosphorus and zinc in the lubricating oil are deposited in the catalyst orifice, the catalyst orifice becomes narrow or partially blocked, the engine exhaust back pressure increases leading to a sharp deterioration of engine combustion, and pollutant emissions will increase by tens or even hundreds of times.
The catalysts used in new cars can only solve the emission problem for at most 10% of the vehicle’s life, while 90% of the time the emission problem must be solved by replacing the catalyst. In particular, the catalysts in cabs with high intensity of use will expire in less than a year.
“Currently, about 80% of motor vehicles in China are equipped with catalysts. According to national regulations, the catalyst life span to meet the National II, National III, National IV and National V emission standards is designed to last 80,000, 80,000, 100,000 and 160,000 kilometers respectively, and it is clearly stipulated that the catalyst cannot become a failure device.” Chen Yaoqiang said, in other words, the number of times the catalyst should be replaced from new to end-of-life is, respectively, National II, National III, National IV and National V should be replaced at least 10 times, 10 times, 8 times and 5 times respectively, “to ensure that the emissions meet the emission standards during the whole life.”
It is estimated that 20% of the vehicles in use should have their catalysts replaced every year. However, “China has not effectively replaced the expired catalysts since the implementation of the National II emission standard for gasoline vehicles in 2003, and a large number of highly polluting vehicles with expired catalysts have accumulated across the country.” Chen Yaoqiang believes that a large part of the hazy weather in the country earlier this year was caused by the pollution emitted by a large number of seriously over-standard vehicles with expired catalysts that have not been replaced.
Establishment of motor vehicle emissions testing stations and maintenance stations
According to reports, countries around the world require that expired catalysts must be replaced on time and implement a strict penalty system. In the United States, failure to replace the catalyst in a timely manner, the gasoline car fines twenty-five thousand dollars, diesel car fines thirty-four thousand dollars; in Canada, the special environmental protection vehicle license plate marked the next catalyst replacement time, such as more than a day penalty of one hundred Canadian dollars, while the replacement of catalytic converters for 300 Canadian dollars; in Mexico, the provision of substandard catalyst fine of 600,000 pesos (about 300,000 yuan).
At present, China has made provisions for motor vehicle emission limits, testing standards, and testing/maintenance systems. Chen Yaoqiang suggested that motor vehicle emission testing stations and maintenance stations with independent legal personality, not belonging to any government agency and operating independently should be established, i.e. a company can only establish testing stations or maintenance stations, not both, in order to maintain impartiality. Government departments are responsible for making regulations, such as testing standards, operation specifications, implementation rules, fees and penalty systems for testing stations and maintenance stations.
“If the qualified catalysts can be successfully replaced, which is equivalent to turning all the high-emission vehicles accumulated from 2003 to now into emission-qualified vehicles, then it is possible to achieve an 80 percent reduction in urban air pollutants in the short term.”
